Known apparatuses for finishing surfaces include rotary finishing tools that rotatingly drive a disc assembly. The disc assembly includes a disc presenting an abrasive material for contacting a surface when the assembly is rotated by the rotary finishing tool. Known disc assemblies include flap discs, such as disclosed in U.S. Pat. No. 5,752,876, which include a plurality of abrasive flaps adhesively secured about the periphery of a backing disc in an overlapping manner.
Known disc assemblies also include a nut having an internally threaded bore for engaging an externally threaded shaft of a rotary power tool. U.S. Pat. No. 4,541,205 (Patrello) discloses a disc assembly including a disc-shaped abrasive wheel and an internally-threaded nut. A portion of the abrasive wheel adjacent an inner edge of the wheel is covered by ring-like bushings and contained within a notch defined by the nut and an integral retainer that is outwardly rolled over the grinding wheel. The disc assembly of Patrello also includes a reinforcing dish connected to the nut. As shown in FIGS. 1 and 5, the dish extends radially outwardly from the nut to cover a substantial part of the rear surface of the grinding wheel. The added reinforcement provided by the dish functions to distribute applied loads between the nut and the grinding wheel to avoid damage to the inner portion of the grinding wheel.
Other known disc assemblies include separate reinforcing members, such as washers, instead of the above-described integral dish of Patrello, to distribute load between a nut and a disc member of the assembly to avoid damage to an inner radial portion of the disc member.